Spending watchdog the National Audit Office said normal schools suffered when Michael Gove’s Department for Education raided other budgets to up the number of academies from 203 in 2010 to 2,309 today.

It blasted the Department for being “unprepared for the financial impact of rapid expansion”, adding the number of staff needed to run the scheme leapt from 120 in 2010/2011 to 280 in 2011/12 – an increase of 133%.

The NAO also criticised the Government for relying on academies’ finance bosses to make sure public money was used properly and legally.

It warned that were any mismanagement found, the entire scheme would be thrown into crisis.

NAO chief Amyas Morse said: “The Department must build on efforts to reduce costs and tackle ­accountability concerns if it is to reduce the risks.”

The Department claimed academies would improve standards, but the Association of Teachers and Lecturers said it was too early to know.

General secretary Dr Mary Bousted added: “There appears to be no limit to the amount of money the Government will pour into this.”

Labour said the report raised “serious questions” and called for greater scrutiny to ensure value for money.